1. Technical Field
The present invention relates generally to insulated chambers such as incubators, environmental chambers, freezers, refrigerators and ovens. More particularly, the present invention relates to an insulated chamber in which a phase change material enhances temperature control.
2. Background Information
Insulated chambers may be used for a variety of purposes. For instance, such chambers may include incubators, environmental chambers, freezers, refrigerators and ovens. Incubators are typically used for growing cultures in a controlled environment, wherein temperature, humidity, and atmospheric gas concentration are maintained at selected levels. For certain applications it is highly desirable to have both temperature and gas concentrations maintained within strict tolerances while still allowing easy access to the incubator chamber for adding or removing items to and from the chamber or for inspecting the contents of the chamber. Control of environmental variables is desirable to maintain accuracy and reproducibility of incubation results. Typical incubators have used either open-coil heaters within the incubator chamber or water jackets surrounding the incubator chamber. However, while such configurations can be effective in heating an incubator, they do not necessarily provide as strict a control on the incubator temperature as is desirable for consistent results.
Conventional air heater type incubators lack the temperature stability of the water jacket type. Water-jacketed incubators maintain temperature by surrounding the interior chamber with heated water in a separate compartment. The water is heated and circulates around the inner chamber via natural convection. The heat from the water radiates to the interior chamber to maintain a substantially constant temperature inside. Water is an effective thermal insulator and the water-jacket system is considered a more reliable method of heating in case of a power outage. In the wake of a power failure, a water-jacketed incubator will hold a set temperature inside the chamber 4-5 times longer than a radiant-walled unit.
Radiant-walled incubators heat the interior chamber using heaters mounted in the surrounding cavity that radiate heat through to the inside chamber. A radiant-walled heating system allows for quick recovery of temperature following door openings or changes in temperature settings. Radiant-walled heating systems are also more simplified for the user, not requiring filling, monitoring, and emptying water in the water jacket.
A fan may be mounted outside of the culturing area to help to circulate the air inside the chamber without disturbing cultures. This gentle circulation helps maintain a consistent temperature throughout the chamber and speeds recovery of internal temperature as well as CO.sub.2 and humidity levels following door openings.